ffi 3.2 C1: migrate uikit.sx Foundation utility cluster to #objc_class

First of five Phase-3.2 migration clusters. Foundation utility
classes (NSValue, NSNumber, NSDictionary, NSMutableDictionary, NSSet)
in `library/modules/platform/uikit.sx` move from the explicit
`#objc_call(T)(recv, "selector:", args)` form to declarative
`#foreign #objc_class("Cls") { ... }` blocks with `recv.method(args)`
dispatch.

Classes declared (all near the top of uikit.sx, after the CGRect
struct):

- NSValue          → CGRectValue (instance)
- NSNumber         → numberWithBool (class), doubleValue +
                     unsignedLongValue (instance)
- NSDictionary     → objectForKey (instance)
- NSMutableDictionary → dictionary (class), setObject_forKey (instance)
- NSSet            → anyObject (instance)

Each call site casts the `*void` receiver to the typed foreign-class
pointer before dispatch — the existing `*void` shape is preserved
in the struct fields and outer parameter types; only the dispatch-
local copy is typed. This keeps the diff scoped to call-site
rewrites without rippling type changes through every consumer.

The four `objc_getClass(...)` calls that previously resolved
NSMutableDictionary / NSNumber at runtime are gone — Phase 3.1's
`__sx_objc_class_init` constructor populates the cached class slot
for each declared `#objc_class` at module load via
`OBJC_CLASSLIST_REFERENCES_<Cls>`.

166/166 example tests; chess clean on macOS + Android via
`tools/verify-step.sh` (iOS sim skipped — no booted simulator in
this run; previous full run was green at HEAD~6).

current/CHECKPOINT-FFI.md

@@ -543,8 +543,18 @@ one fixture. Both `.txt` and `.ir` snapshots locked — a change to
 `deriveObjcSelector` produces one diff that surfaces every affected
 case at once via the `OBJC_METH_VAR_NAME_*` constants in the IR.
 
-Open work, in roughly the order they make sense:
+Phase 3.2 C1 landed: Foundation utility cluster in uikit.sx
-- **Phase 3 step 3.2 — C1..C5** — uikit.sx migration, one cluster
+migrated to declarative `#objc_class` bodies. Five classes declared
+near the top of the file (NSValue, NSNumber, NSDictionary,
+NSMutableDictionary, NSSet). Call sites rewritten from
+`#objc_call(T)(recv, "sel:", args)` to `recv.method(args)` /
+`Cls.method(args)`. Receivers cast from `*void` to the typed
+foreign-class pointer at the dispatch site. The `objc_getClass(...)`
+calls for these classes are gone — the class slot is now populated
+by emit_llvm's `__sx_objc_class_init` constructor (Phase 3.1).
+
+Open work:
+- **Phase 3 step 3.2 — C2..C5** — uikit.sx migration, one cluster
   per commit, chess regression after each.
   test for the default-mangling table. Escape hatch for selectors
   that don't fit the underscore-split rule (e.g. `tableView_

library/modules/platform/uikit.sx

@@ -52,6 +52,38 @@ CGRect :: struct {
     height: f64;
 }
 
+// ── Foundation utility classes (Phase 3.2 C1) ─────────────────────────
+// Declarative `#objc_class` bindings replace the previous
+// `objc_getClass(...) + #objc_call(T)(...)` pattern. Each method's sx-
+// side name maps to its Obj-C selector via the default mangling rule
+// (split on `_`; each piece becomes a keyword with `:`).
+
+NSValue :: #foreign #objc_class("NSValue") {
+    // CGRect unboxing — returns by value via the sret/HFA path.
+    CGRectValue :: (self: *Self) -> CGRect;
+}
+
+NSNumber :: #foreign #objc_class("NSNumber") {
+    // Class method (no `self: *Self` first param → static dispatch).
+    numberWithBool :: (b: s8) -> *NSNumber;
+    // Instance value extractors.
+    doubleValue        :: (self: *Self) -> f64;
+    unsignedLongValue  :: (self: *Self) -> u64;
+}
+
+NSDictionary :: #foreign #objc_class("NSDictionary") {
+    objectForKey :: (self: *Self, key: *void) -> *void;
+}
+
+NSMutableDictionary :: #foreign #objc_class("NSMutableDictionary") {
+    dictionary         :: () -> *NSMutableDictionary;
+    setObject_forKey   :: (self: *Self, obj: *void, key: *void);
+}
+
+NSSet :: #foreign #objc_class("NSSet") {
+    anyObject :: (self: *Self) -> *void;
+}
+
 // GLenum constants for renderbuffer/framebuffer setup that aren't in opengl.sx's
 // loader path (they live on the framework's symbol table directly).
 GL_RENDERBUFFER          :u32: 0x8D41;
@@ -356,23 +388,28 @@ uikit_keyboard_will_change_frame :: (self: *void, _cmd: *void, notification: *vo
     if g_uikit_plat == null { return; }
     plat := g_uikit_plat;
 
-    user_info := #objc_call(*void)(notification, "userInfo");
+    user_info_raw := #objc_call(*void)(notification, "userInfo");
-    if user_info == null { return; }
+    if user_info_raw == null { return; }
+    user_info : *NSDictionary = xx user_info_raw;
 
-    end_value := #objc_call(*void)(user_info, "objectForKey:",
+    end_value_raw := user_info.objectForKey(ns_string("UIKeyboardFrameEndUserInfoKey".ptr));
-        ns_string("UIKeyboardFrameEndUserInfoKey".ptr));
+    if end_value_raw == null { return; }
-    if end_value == null { return; }
+    end_value : *NSValue = xx end_value_raw;
-    end_rect := #objc_call(CGRect)(end_value, "CGRectValue");
+    end_rect := end_value.CGRectValue();
 
-    dur_value := #objc_call(*void)(user_info, "objectForKey:",
+    dur_value_raw := user_info.objectForKey(ns_string("UIKeyboardAnimationDurationUserInfoKey".ptr));
-        ns_string("UIKeyboardAnimationDurationUserInfoKey".ptr));
     anim_dur : f64 = 0.0;
-    if dur_value != null { anim_dur = #objc_call(f64)(dur_value, "doubleValue"); }
+    if dur_value_raw != null {
+        dur_value : *NSNumber = xx dur_value_raw;
+        anim_dur = dur_value.doubleValue();
+    }
 
-    curve_value := #objc_call(*void)(user_info, "objectForKey:",
+    curve_value_raw := user_info.objectForKey(ns_string("UIKeyboardAnimationCurveUserInfoKey".ptr));
-        ns_string("UIKeyboardAnimationCurveUserInfoKey".ptr));
     curve_int : u64 = 0;
-    if curve_value != null { curve_int = #objc_call(u64)(curve_value, "unsignedLongValue"); }
+    if curve_value_raw != null {
+        curve_value : *NSNumber = xx curve_value_raw;
+        curve_int = curve_value.unsignedLongValue();
+    }
 
     // Screen height in points. The window lives on the connected scene's screen.
     if plat.window == null { return; }
@@ -520,10 +557,7 @@ uikit_scene_will_connect_ios :: (delegate: *void, scene: *void) {
         // EAGLContext.renderbufferStorage:fromDrawable: (color format,
         // non-retained backing). Without this dict the renderbuffer
         // allocation silently fails and the framebuffer reports INCOMPLETE.
-        NSMutableDictionary := objc_getClass("NSMutableDictionary".ptr);
+        ns_no := NSNumber.numberWithBool(0);
-        NSNumber            := objc_getClass("NSNumber".ptr);
-
-        ns_no := #objc_call(*void)(NSNumber, "numberWithBool:", xx 0);
 
         // The EAGL dict keys/values must be the framework-provided NSString
         // constants (pointer identity is checked) — dlsym them from OpenGLES.
@@ -531,10 +565,10 @@ uikit_scene_will_connect_ios :: (delegate: *void, scene: *void) {
         colorformat_key := uikit_extern_nsstring("kEAGLDrawablePropertyColorFormat".ptr);
         rgba8_value    := uikit_extern_nsstring("kEAGLColorFormatRGBA8".ptr);
 
-        dict := #objc_call(*void)(NSMutableDictionary, "dictionary");
+        dict := NSMutableDictionary.dictionary();
-        #objc_call(void)(dict, "setObject:forKey:", ns_no,       retained_key);
+        dict.setObject_forKey(xx ns_no, retained_key);
-        #objc_call(void)(dict, "setObject:forKey:", rgba8_value, colorformat_key);
+        dict.setObject_forKey(rgba8_value, colorformat_key);
-        #objc_call(void)(plat.gl_layer, "setDrawableProperties:", dict);
+        #objc_call(void)(plat.gl_layer, "setDrawableProperties:", xx dict);
     }
 
     // EAGLContext + load_gl were already done in uikit_create_gl_context()
@@ -732,7 +766,8 @@ uikit_touch_location :: (touch: *void, view: *void) -> Point {
 }
 
 uikit_first_touch :: (touches: *void) -> *void {
-    #objc_call(*void)(touches, "anyObject");
+    touches_set : *NSSet = xx touches;
+    touches_set.anyObject();
 }
 
 uikit_gl_view_touches_began :: (self: *void, _cmd: *void, touches: *void, event: *void) callconv(.c) {